交联聚乙烯电缆水树修复前后电缆微观结构的变化

针对XLPE电缆绝缘层水树区修复前后的微观结构变化,本文主要利用红外光谱检测技术(Fourier Transform Infrared Spectroscopy, FTIR)观测新样本、老化样本和修复样本分子结构的变化,并阐明其变化原因。老化样本的红外光谱检测结果显示老化样本中水树区甲基(—CH3)、羟基(—OH)基团含量增加,C=O键吸收峰强度加强。说明在电缆老化过程中,电缆XLPE绝缘层存在分子键断裂和氧化降解。而在修复样本的红外光谱中,发现甲基、羟基和C=O键吸收峰强度明显地减弱,C-Si键吸收峰的强度略微增强。同时,利用扫描电镜(SEM)和X射线能谱分析仪对修复样本水树区进行分析,发现水树区中硅元素的原子百分比和重量百分比增加。即修复后电缆水树区的化学元素含量和分子结构发生改变,从而影响了电缆绝缘性能。

Microstructure Changes of XLPE Cable in Water Tree Area Before and After Injection Rejuvenation

For microstructure changes of XLPE cable insulation layer, this paper analyzes insulation layer of the new samples, aged samples and rejuvenation samples by Fourier Transform Infrared Spectroscopy (FTIR), and analyzes the causes. Compared with the new sample, the methyl (-CH3) groups and hydroxyl (-OH) groups are increasing and the absorption peak intensity of the carbon-oxygen double bond (C=O) is strengthening in the insulating layer of aged samples. These chemical changes indicate that molecular bond breaking, oxidation degradation and other chemical changes occur in water tree during the process of aging. Furthermore, the absorption peak intensity of the methyl groups, hydroxyl groups and carbon-oxygen double bond spectra indicate a decrease after rejuvenation. However, the absorption peak intensity of C-Si bond is strengthening. Meanwhile, qualitative analysis for chemical elements in water tree is tested by scanning electron microscope and X-ray photoelectron spectroscopy. The results reveal that atomic percentage and weight percentage of Si increase in water tree area. Consequently, the content of chemical elements and molecular structure occur changes in water tree after rejuvenation.